Why does returning nil from
UICollectionViewDiffableDataSource<FeedElement, Entity>(collectionView: collectionView) {
(collectionView: UICollectionView, indexPath: IndexPath, entity: Entity) -> UICollectionViewCell? in
result n "the collection view's data source did not return a valid cell from"
Isn't the UICollectionViewCell optional?
nomspes
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I can't seem to get UICollectionViewDataSourcePrefetching working with DiffableDatasource, my delegate methods are not being called. Do these work together?
		func viewDidLoad()
				....
collectionView.prefetchDataSource = self
collectionView.isPrefetchingEnabled = true
		}
extension ViewController: UICollectionViewDataSourcePrefetching {
func collectionView(_ collectionView: UICollectionView, prefetchItemsAt indexPaths: [IndexPath]) {
let urls: [URL] = indexPaths.compactMap { indexPath in
guard let displayableItem = dataSource.itemIdentifier(for: indexPath),
let itemViewModel = displayableItem.item as? ViewModel,
let image = itemViewModel.firstImageURL else {
return nil
}
return image
}
ATHLogging.log.critical("prefetching: \(urls)")
preheater.startPreheating(with: urls)
}
There is a black bar at the top of my Widget and I can't seem to figure out how to get rid of it.
struct A1EntryView : View {
var entry: Provider.Entry
var body: some View {
Text("Temp")
.frame(maxHeight: .infinity)
.background(Color(.red))
.ignoresSafeArea(.all)
}
}
I have a crash happening when applying a snapshot. 9/10 times its seems to work.
When we re-fetch backend data, and apply the snapshot sometimes we get the follow crash
the view returned from -collectionView:viewForSupplementaryElementOfKind:atIndexPath (cover-edge-trailing-element-kind,<NSIndexPath: 0xf45fd089cda10b3f> {length = 2, path = 55 - 1}) was not retrieved by calling -dequeueReusableSupplementaryViewOfKind:withReuseIdentifier:forIndexPath: or is nil ((null))
We don't call this function, as it seems to be done by the diffable datasource.
Fatal Exception: NSInternalInconsistencyException
0	CoreFoundation								 0x1b75c2300 __exceptionPreprocess
1	libobjc.A.dylib								0x1b72d6c1c objc_exception_throw
2	CoreFoundation								 0x1b74bf1f8 +[_CFXNotificationTokenRegistration keyCallbacks]
3	Foundation										 0x1b7903998 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
4	UIKitCore											0x1baf133dc -[UICollectionView _createPreparedSupplementaryViewForElementOfKind:atIndexPath:withLayoutAttributes:applyAttributes:]
5	UIKitCore											0x1baf2dc6c -[UICollectionView _viewAnimationsForCurrentUpdate]
6	UIKitCore											0x1baf31d68 __71-[UICollectionView _updateWithItems:tentativelyForReordering:animator:]_block_invoke.2004
7	UIKitCore											0x1bbbcf5d8 +[UIView(Animation) performWithoutAnimation:]
8	UIKitCore											0x1baf30f2c -[UICollectionView _updateWithItems:tentativelyForReordering:animator:]
9	UIKitCore											0x1baf2b488 -[UICollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:animator:]
10 UIKitCore											0x1baf32f4c -[UICollectionView _endUpdatesWithInvalidationContext:tentativelyForReordering:animator:]
11 UIKitCore											0x1baf332d0 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:animator:]
12 UIKitCore											0x1baf33100 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:]
13 UIKitCore											0x1baf3307c -[UICollectionView _performBatchUpdates:completion:invalidationContext:]
14 UIKitCore											0x1baf32fa8 -[UICollectionView performBatchUpdates:completion:]
15 UIKitCore											0x1baf41268 -[UICollectionView _performDiffableUpdate:]
16 UIKitCore											0x1baee7e6c -[_UIDiffableDataSourceViewUpdater _performUpdateWithCollectionViewUpdateItems:dataSourceSnapshotter:updateHandler:completion:]
17 UIKitCore											0x1baee10f4 -[__UIDiffableDataSource _commitNewDataSource:withViewUpdates:completion:]
18 UIKitCore											0x1baedc0c0 66-[UIDiffableDataSource applyDifferencesFromSnapshot:completion:]_block_invoke.154
19 UIKitCore											0x1baedc388 66-[UIDiffableDataSource applyDifferencesFromSnapshot:completion:]_block_invoke.183
20 libdispatch.dylib							0x1b726233c _dispatch_client_callout
21 libdispatch.dylib							0x1b726f1f4 _dispatch_lane_barrier_sync_invoke_and_complete
22 UIKitCore											0x1baedbba8 -[__UIDiffableDataSource applyDifferencesFromSnapshot:completion:]
23 UIKitCore											0x1baedcc68 -[__UIDiffableDataSource applyDifferencesFromSnapshot:animatingDifferences:completion:]
24 libswiftUIKit.dylib						0x1edef8030 UICollectionViewDiffableDataSource.apply(_:animatingDifferences:completion:)
25 theathletic-ios								0x105048b60 closure #1 in RealTimeContentsViewController.fetchData(with:newWatcher:) + 137 (RealTimeContentsViewController.swift:137)
26 theathletic-ios								0x10504b48c RealTimeContentsViewController.updateDataSource(for:completion:) + 265 (RealTimeContentsViewController.swift:265)
27 theathletic-ios	
Heres how we are registering, creating, and supplying the view
static let coverEdgeTrailingIdentifier = "cover-edge-trailing-element-kind"
collectionView.register(
CoverEdgeCollectionReusableView.self,
forSupplementaryViewOfKind: K.coverEdgeTrailingIdentifier,
withReuseIdentifier: CoverEdgeCollectionReusableView.reuseIdentifier)
dataSource.supplementaryViewProvider = { (
collectionView: UICollectionView,
kind: String,
indexPath: IndexPath) -> UICollectionReusableView? {
return collectionView.dequeueReusableSupplementaryView(
ofKind: kind,
withReuseIdentifier: CoverEdgeCollectionReusableView.reuseIdentifier,
for: indexPath) as! CoverEdgeCollectionReusableView
}
I have two section backgrounds for my compositional layout.
layout.register(
FollowingSectionBackgroundView.self,
forDecorationViewOfKind: FollowingCollectionViewController.sectionBackgroundDecorationFollowing)
layout.register(
BrowseSectionBackgroundView.self,
forDecorationViewOfKind: FollowingCollectionViewController.sectionBackgroundDecorationBrowse)
And I configure them like so in my UICollectionViewCompositonaLayoutClosure
if sectionIndex == 0 {
let sectionBackgroundDecoration = NSCollectionLayoutDecorationItem.background(
elementKind: FollowingCollectionViewController.sectionBackgroundDecorationFollowing)
section.decorationItems = [sectionBackgroundDecoration]
} else {
let sectionBackgroundDecoration = NSCollectionLayoutDecorationItem.background(
elementKind: FollowingCollectionViewController.sectionBackgroundDecorationBrowse)
section.decorationItems = [sectionBackgroundDecoration]
}
And this seems to be working just fine, however I have seen crashes uploaded that say:
Fatal Exception: NSInternalInconsistencyException
no UICollectionViewLayoutAttributes instance for -layoutAttributesForDecorationViewOfKind: section-background-browse at path <NSIndexPath: 0xfe6f76a7b11ddfee> {length = 2, path = 0 - 0}
The crash appears to happen when the user searches.
isSearching = true
let following = FollowingController.filterBrowse(with: filter).sorted { $0.name < $1.name }
var snapshot = NSDiffableDataSourceSnapshot<SectionLayoutKind, FollowingEntity>()
snapshot.appendSections([.browse])
snapshot.appendItems(following)
dataSource.apply(snapshot, animatingDifferences: true)
Im unable to reproduce this issue but just curious if anyone has run into this, and might have an idea for solving it.